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	DOMContentLoaded 原生当中实现dom加载的事件  826行
	<div id="box1">fusdfhi</div>

	829行的时候有个定时器 
		if ( document.readyState === "complete" ) {
			// Handle it asynchronously to allow scripts the opportunity to delay ready
			setTimeout( jQuery.ready );  //为了防止IE的IE会提前触发
		}
		else {

			// Use the handy event callback
			document.addEventListener( "DOMContentLoaded", completed, false );

			// A fallback to window.onload, that will always work
			window.addEventListener( "load", completed, false );
		}
		为什么会检测两个？
		因为有的浏览器会缓存load,所以有缓存了先触发这个load的事件，不管走哪个都调用completed
		

		在90行的时候
		completed = function() {
			document.removeEventListener( "DOMContentLoaded", completed, false );
			window.removeEventListener( "load", completed, false );
			jQuery.ready();
		};
		只要执行这个completed这个方法，先去取消两个事件，jQuery.ready();只会触发一次


		$.ready --> 有个readyList.resolveWith( document, [ jQuery ] );

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